1. Field of the Invention
The present invention relates to a control circuit for assisting operator effected storage of a hydraulically operated articulated work arm into an "over center" storage position. By permitting simplified operation of the work arm into the storage position, the functionality of the apparatus is increased. The control circuit includes an electrically operated valve, which may be a solenoid valve, that is operably connected to the hydraulic operating system of the work arm. Further, the control circuit includes a controller for the solenoid so that operation of the work arm into various selected positions is simplified.
2. Description of Related Art
Mobile construction equipment such as tractors outfitted with a hydraulically operated articulated work arm carrying any one of a variety of attachments are used for a wide variety of applications. In particular, they are critical machines in the construction of buildings, transportation channels, and almost any other man-made structure. A practical matter involves the transport of such equipment, such as, for example, a backhoe between the physical locations where it will be used. If the equipment is driven to the desired location over roadways, difficulties associated with the weight distribution of the equipment often arise. In particular, the overhanging, leveraged weight of the backhoe linkage assembly increases the difficulty of controlling the equipment during transportation. The effective weight of the backhoe linkage assembly can affect equipment weight balance sufficiently such that the weight remaining on the front wheels is lessened and steering control and ride comfort may be compromised.
To date, the most common approach to dealing with the undesirable weight distribution of this type of construction equipment is to add weight to the front of the machine to counter the weight of the backhoe linkage assembly. However, this solution is undesirable for several reasons. The additional weight causes the equipment to become more difficult to maneuver, especially in soft ground, more difficult to steer, and more clumsy to operate. In addition, fuel consumption is increased and the equipment cost effectiveness is decreased.
A more desirable solution to the problem of weight distribution has been to move the backhoe linkage assembly into a stored position where its weight is closer to the center of the equipment. For example, Case Corporation of Racine, Wisconsin builds backhoe-type machines with a distinctive feature, known as an "over center" system, that permits the weight of the backhoe to be moved closer to the center of the equipment, whereby the weight moment arm is reduced. By shifting the weight of the backhoe toward the equipment's center of gravity, the need for a front-end counter weight is eliminated. The "over center" position of the backhoe linkage assembly is frequently known as the "carry," the "latched," or the "transport" position. The "over center" system, as noted above, increases the maneuverability of the equipment, particularly in soft ground, and increases the stability of the equipment during road transportation.
While the "over center" system provides significant benefits, use of the system requires operator skills that are acquired only through experience. Thus, while not always difficult for regular users of the equipment, the technique may often be awkward for new or occasional users of the machine. The technique involves a combination of operator actions that must be completed in timed sequence. The technique of moving the backhoe into the "over center" position requires the operator to activate the lift cylinder and raise the work arm toward its uppermost position. At the moment that the lift cylinder is at its minimum length, the operator must then rapidly change the direction of the hydraulic control spool to reverse the direction of the lift cylinder operation to thereby drive the backhoe into the "over center" transport position. If the control spool is not operated at the right moment, the backhoe assembly will stop moving and will not reach the transport position. The entire process must then be repeated. First time operators and operators without significant experience often have difficulty performing the technique.
The present invention for the first time provides an apparatus for reducing the heretofore important nature of operator performance in placing equipment work arms into the over-center storage/transport position. Thus, new and less experienced operators can prepare the backhoe for travel between work sites.